IC INDUSTRY AWARDS WINNER 2008
9
Award: Wafer Processing - Best Process
Company: Surface Technology Systems Plc
Process: Pegasus DRIE technology for 3D packaging applications
Website: www.stsystems.com
Pegasus DRIE technology for
3D packaging applications
B
uilding on over a decade's Another undesirable characteristic of the Bosch
experience in deep reactive ion Process is the “scalloping” of the via sidewall,
etching (DRIE) of silicon for caused by the isotropic nature of each short
MEMS manufacturing, STS latest DRIE SF6 etch step.
system, named "Pegasus", has proved to be a
successful, enabling plasma etch tool not only The shorter the etch step, the smaller the
in the MEMS industry but also in through “scallop” - giving smoother sidewalls. Sidewall
silicon via (TSV) etching in emerging advanced roughness should be minimised in TSV etching
3D-IC packaging applications. because a rough sidewall could cause problems
with subsequent via hole filling steps. STS’
Launched in September 2005, STS’ Pegasus Pegasus system minimizes sidewall roughness
system utilizes the “Bosch Process” which is a through a combination of hardware and
well established method of anisotropically software features which allow very fast
etching deep, high aspect ratio features into switching between the passivating and etch
silicon, switching between a passivating C4F8 plasmas. This means that each individual etch
plasma and a reactive SF6 plasma. This dry step can be very short, giving smooth sidewalls
plasma process offers significant advantages without reducing the total etch time, and
over the competing laser drilling technique, consequently the overall etch rate is not
particularly when via holes are <10um and via adversely affected.
hole densities are high.
Pegasus has now proved itself to be a
Pegasus has a unique plasma source design commercially successful product, with an
which offers market-leading silicon etch rates, installed base of over 100 plasma chambers
typically 30% faster than conventional de- sold by STS and parent company Sumitomo
coupled "high rate" plasma sources. This high Precision Products Co, Ltd in less than 3 years.
etch rate increases throughput, reducing cost Many of the systems have been multi-chamber
per die. cluster tools for high volume manufacturing
applications. With its high silicon etch rate,
Another important factors when etching very control of plasma uniformity and fast plasma
deep features such as via holes into silicon is switching capabilities, Pegasus offers truly
that conventional DRIE sources tend to have enabling capabilities to companies investigating
non-uniform plasma characteristics across the new ways of packaging devices using through
wafer, which can lead to feature tilting and a silicon via etching in 3D-IC / wafer-stacking
corresponding reduction in device yield, applications.
particularly for large diameter wafers typically
used in 3D packaging applications. Coupled with industry-standard Brooks
handling cluster platforms, the Pegasus
Pegasus has been designed in such a way to provides these market-leading process
minimise this effect by careful control of the capabilities with production-proven wafer
plasma conditions (including ions, electrons and handling, all combining to reduce cost per die
radicals) across the whole wafer surface. for the final end product.
IC Industry Award Winners 2008 www.euroasiasemiconductor.com
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